Multi-Element Resonant Converters

Abstract

A resonant switched power converter having switching frequency controlled in response to an output voltage thereof achieves over-current protection such as at start-up or under short circuit conditions using a resonant tank circuit which provides a notch filter in addition to a band pass filter. A additional band pass filter provided in the resonant tank circuit achieves increased power transfer to a load and reduced circulating resonant currents and conduction losses. The inductances of the preferred LCLCL tank circuit or other tank circuit with two pass band filters and a notch filter may be integrated into a single electrical component.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention generally relates to power supply systems and voltage converters and, more particularly, to resonant DC / DC converters and power supplies having four or more resonating elements to achieve both increased efficiency and other desired characteristics such as start-up and short-circuit over-current protection.[0003]2. Description of the Prior Art[0004]Many currently available and foreseeable commercial electronic products provide for operation from DC power sources such as rechargeable batteries but also provide for obtaining power from commonly available AC distribution systems. Many such devices include digital logic circuitry which may be of a wide range of complexity and which may include technologically advanced components with stringent tolerances for voltage and current requirements including widely varying current demands at very low voltages such as are encountered in providing power to microp...

AI Technical Summary

Benefits of technology

[0012]In order to accomplish these and other objects of the invention, a multi-element DC / DC power converter is provided comprising a switched power input circuit and a resonant tank circuit comprising at least four elements, said resonant tank circuit providing a band pass filter resonant at a first frequency, a notch filter resonant at a second frequency higher than said first frequency. A further band pass filter resonant at a frequency which is a harmonic of the first frequency can increase power transfer to a load at harmonics of the switching frequency. All required inductive and transformer elements can also be integrated into a single electrical component.

Problems solved by technology

However, the efficiency which can be achieved by hard-switching converters is limited by the switching losses which become especially severe as switching frequencies are increased.

However, the resonant circuit causes large currents to circulate within the converter, particularly at harmonics of the switching frequency, and conduction losses can be significant.

Therefore, bulky capacitors are used to provide energy during the holdup time.

Thus the capacity of the holdup time capacitor is wholly determined by required energy during holdup time and severely limits the capability for increasing increased power density even though increasing the operating range can extract more power from the holdup capacitor and allow a capacitor of somewhat reduce value to be employed.

Unfortunately, sacrifice of a significant degree of efficiency is required to extend the operating range in order to do so through known techniques.

While some arrangements have been proposed for extending operational range and extending holdup time for a given capacitance, they are complex and difficult to control.

While LLC converters can achieve zero voltage switching (ZVS) and zero current switching (ZCS) together with high voltage gain capability suitable for reducing the holdup capacitance requirement, currents during start up and short circuit conditions excessively stresses internal components, compromising reliability.

Further, the magnitude of circulating resonant currents is aggravated; imposing an increased limitation of efficiency.

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